Device for gettering metal tubes



Jan. 12, 1937. J. E. BEGGs a 2,067,817

DEVICE FOR GETTERING METAL TUBES I Filed sept. 15, 1954V Invent or James Bfe s,

H s Att-,ovh ey.

Patented Jan. l2, 1937 UNITED STATES 2,067,817 DEVICE FOR GETTERING MCETAL TUBES James E. Beggs, Schenectady, N. Y., assignor to General Electric Company, a vcorporation of New York Application September 15, 1934, Serial No. 744,166

11 Claims.

The present invention relates to thermionic devices of the metal envelope type and more particularly to the art o f gettering such devices.

An object of the invention is to provide a satisfactory and inexpensive arrangement for improving the vacuum of metal tubes. Other objects areY to improve the gettering of such, tubes, and more particularly to` mount getter material in an envelope in such a manner that it may be flashed from the exterior of the envelope. A further object is to provide structure for preventing the getter material from reaching the electrodes and conductors Within the envelope.

In the drawing, Fig. 1 is a view, partly in section, of a typical tube improved in accordance with the present invention; Fig. 2 is a sectional view of a preferred form of cathode employed in the tube shown in Fig. 1; Fig. 3 illustrates am improved typical seal for insulatingly and hermeticallysealing one of the leading-in conductors in the metal envelope; Fig. 4 is a view taken along line 4-4 in Fig. 1, locking in the direction of the arrows; and Fig. 5 is a` sectional view of the upper portion vof, a pentode device, illusrating a modied method of gettering a metal ube.

Referring more particularly to Fig.y 1, numeral I designates an envelope of cylindrical conguration and constituted of a workable, inexpensive metal such as iron or nickel. The upper end of the envelope is closed by a flat portiorr 2 which may be formed integral with the envelope by a deep-drawing process, and the lower end is closed by a metal header 3, preferably of the same metal as the envelope. This header takes the form of a reentrant member provided with a deep flange which may be welded to the interior surface of the envelope.

In addition to the electrode structure which will be described presently, the header 3 carries a metal seal-off'tube 4 through which the interior of the envelope may be evacuated and nally sealed oif from the pump in the manner disclosed and claimed in the Nolte application, Serial No. 743,832, filed September 13, 1934 entitled Metal vacuum tubes and assigned to the same assignee as the present application.

'Ihe invention has been illustrated in Fig. 1z in connection With a three-electrode device constituted of a cathode 5, a helical grid 6 and an anode 1, all concentrically arranged and supported in any suitable manner between a pair of mica disks 8 which t snugly within the en.E

velope. 'I'he cathode preferably is of the indirectly heated type and as shown in Fig. 2, may consist of a heater 9 of tungsten, embedded in a mass of insulating material IIJ and contained within a nickel cylinder 6 which constitutes the 5 cathode proper. This cylinder may be coated withA electrionically active material I I such as strontium or barium oxide, obtained from the carbonate, as is well-known in the art.

Leading-in conductors I2 are taken from both ends of the heater and a conductor I3 connected to the cathode 6. One of the uprights I4 of the grid electrode maybe extended through the*4 mica disk to constitute a leading-in conductor for that electrode. A rigid wire I5 .may also be secured to the anode l to' serve as a leading-in conductor. The various leading-in conductors, except the conductor for the cathode, are taken` out through the header 3 by means of improved seals which will be described presently. The leading-in conductor I3 for the cathode is effectively connected to the envelope I in the manner explained hereinafter and for this reason, does not require a seal.

As shown in Fig. 3, 4the header 3 is provided withopenings at the various positions through whichvthe leading-in conductors are to pass and `surrounding each of these conductors, there is a metal eyelet I6 secured to the header. A mass of glass I1 completely fills the space between the leading-in conductor and the metal eyelet, providing a hermetic joint between the conductor and the glass, also between the glass and the eyelet. The seal, including the conductor, eyelet and glass members, is fabricated apart from the header and then secured to the latter. For this purpose, a flange is formed on the eyelet which may be welded, eitherto the upper side or the lower side of the` header member. kThe improved form of seal has been disclosed and broadly claimed in the Elder and Gable application, Serial No. 746,808, filed October 4, 1934 entitledk Electric 'discharge devices and seals therefor, and disclosed and claimed in a limited aspect in my application, Serial No. 744,165, led September 15, 1934 entitled Glass-to-metal seals. The applications referred to are assigned to the same assignee as the present invention.

As pointed out in these applications, the eyelet material and the glass should preferably have the same thermal expansion characteristic over the entire temperature range between 0 C. and the softening temperature of the glass. A typical metal which may be employed for this purpose is 18% cobalt (Co), 28% nickel (Ni) and 54% iron (Fe), while the glass may have the following approximate composition: silica (SiOz), 23% boric oxide (B203), 7% sodium oxide (NazO) and 5% aluminum oxide (Alza). Under some conditions, the metal may consist of molybdenum, nickel or copper, and the glass made of a composition which is sold under the trade name Corning 705 AJ. As many seals are provided as are necessary to take the various leading-in conductors through the metal header.

As stated hereinbefore, the present invention relates to an improved means for gettering tubes of the all-metal type and for this purpose, there is provided at the lower end of the tube as shown, as far from the electrode structure as possible, a circular indentation i8 which forms a pocket immediately above the inner or upper side of the header member 3. In this pocket, there is a getter as indicated, which may consist of any suitable and well-known material, such as magnesium preferably in pellet form. In order to maintain the getter in, position, there is provided a shield I9 which conveniently takes the form of an arcuate strip of metal, spotwelded to the envelope interior. The getter material is placed in the pocket and the shield member i9 welded in position before the header member and the electrodes are mounted in the envelope. It is apparent that the entire electrode structure and header may be assembled and proper connections made between the various leading-in conductors and the respective electrodes while the header member is positioned apart from the envelope.

The header 3 also carries a semi-cylindrical member 20 which is secured to the header by means of an angle piece 2|, the purpose of the member 2U being to protect the various leadingin conductors from the direct blast of the vapor given off by the getter when the latter is flashed in: the manner described presently. The baiile or shield member 20 is of sufficient length or height so as to extend substantially the entire distance between the lower mica member 8 and the upper surface of the header. By extending the length of the baffle as far as possible, the electrodes are also protected from the direct blast of the getter material. The leading-in conductor i3 of the cathode may be secured to the bale member 20 which is also connected to the header member and the envelope. Thus the envelope is maintained at cathode potential.

In order to flash the getter, it is only necessary to torch the exterior surface of the envelope at the position of the bulge formed by the indentation, and this operation is done prior to sealing-off of the metal tube 4.

VInstead of forming a circular indentation in the envelope as shown in Fig. 1, the` envelope may be drawn to a configuration as will provide the necessary pocket for the getter material. Thus in Fig. 5, the upper end of the envelope is illustrated as being provided with a narrow annular groove 22 which forms a convenient pocket for the getter material, as indicated. In this figure, the electrode structure is typically illustrated as taking the form of a pentode, including an indirectly heated cathode 6, a control grid 23, a screen lgrid 24, a suppressor grid 25 and an anode (not shown) The grids are wound on their respective groups of uprights which are properly spaced and supported by means of a mica disk 26. This disk rests against a ledge 21 r metal tubes and assigned to the same assignee as the present invention.

The leading-in conductor 32 for the control grid is taken out through the upper envelope portion in any suitable manner. As illustrated, an improved form of seal 33 is provided for this conductor, as disclosed and claimed in my application, Serial No. 744,165, this seal serving not 4only the purpose of insulating the conductor from the metal envelope in a hermetic manner but also as a spacing abutment for the upper surface of the mica disk 26. The glassy portion of the seal is provided with an annular groove between the glass and the leading-in conductor, also between the glass and the metal eyelet I6 in order to increase the leakage distance'or path, between the conductor and the metal envelope.

The getter may be pressed within the'annulary groove 22 and held there solely by friction. There is a metal plate 3l! provided with openings 3| of relatively small size and equidistantly spaced about by the plate in line with the groove 22. This plate ts snugly within the envelope and has a central opening which tightly embraces the uprights of the suppressor grid. They plate 30 effectively closes off or isolates the space within the groove 22 from the main portion of the envelope which contains the electrode structure, and its purpose is to prevent the direct blast of the getter material from reaching the interior structure. tween these spaces is through the openings 3I\ and consequently the gettering effects of the vapor produced inthe annular groove byA torching or otherwise heating the exterior; of the envelope adjacent the getter, are exerted entirely through-the restricted openings Vand the vapor does not come into direct contact with the electrodes.` c

The claims in this application are directed, in various scope, to the feature of av dent in the envelope for maintaining the material in position, also to the features of a shield and baille member for directing thegetter vapor. vBroader claims on the featureof securing the getter-material to the envelope in any suitable manner are contained in the Nolte application, Serial No. 743,833, filed September 13, 1934 entitled Devices `for gettering metal tubes and assigned to the same assignee as the present invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric discharge devicek comprising a metal envelope containing an electrode and a supporting structure which snugly fits the interior of said envelope, a pocket formed in the envelope, and gettering material in the pocket, said pocket being of suicient depth to accommodate the getter whereby no obstruction is offered by the getter to said supporting structure.

2. An electric discharge device comprising a metal cylinder containing an electrode structure, a leading-in conductor for said structure insulatingly sealed in the envelope, said cylinder being dented to form a pocket, gettering material in The only communication besaid pocket and a baille between said material and the .electrode structure including the leading-in conductor. i

3. An electric discharge device comprising a metal cylinder containing an electrode structure, a leading-in conductor for said structure insulatingly sealed in the envelope, said cylinder being dented to form a pocket, gettering material in said pocket and held therein by a shield, and a baffle between said material and the electrode structure including the leading-in conductor.

4. An electric discharge device comprising a metal cylinder containing an electrode and a supporting structure therefor which snugly fits the interior of said metal cylinder said cylinder being provided on the interior with an annular groove containing a getter, a portion of said groove being of suiiicient depth to accommodate the getter whereby the getter oifers no obstruction to the supporting structure.

5. An electric discharge device comprising a metal cylinder containing an electrode, said cylinder being provided with an annular groove, gettering material in said groove, and a bafe between said gettering material and said electrode.

6. An electric discharge device comprising a cylindrical envelope With an annular groove, an electrode structure in said envelope, gettering material in said groove, a plate covering the groove, said plate being provided with openings whereby the groove and contained gettering material are entirely closed off fro-m the remainder of the envelope and from the electrode structure except for said openings.

7. An electric discharge device comprising an envelope containing an electrode, a dent in the interior surface of the envelope, said envelope being constituted of relatively thin metal and provided with a bulge on the exterior surface corresponding to the dent on the interior surface, and a gettering material in said dent.

8. An electric discharge device comprising a metal envelope containing an electrode structure, a leading-in conductor for said structure, a glass-to-metal seal for insulating said conductor from said envelope, a pocket formed in the envelope remo-te from said seal, and gettering material in said pocket.

9. An electric discharge device comprising a metal envelope containing an electrode structure, a leading-in conductor for said structure, a metal eyelet secured to said envelope, said conductor passing through said eyelet, and a glass member between said eyelet and the conductor and sealed thereto, a pocket formed in the envelope remote from said eyelet, and a getter material in said pocket.

10. An electric discharge device comprising an envelope containing an electrode structure, a leading-in conductor for said structure, a metal eyelet secured to said envelope, said conductor passing through said eyelet, and a glass member between said eyelet and conductor and sealed thereto, a pocket formed in the envelope remote from the seals between said glass member, eyelet and conductor, said envelope being fabricated entirely of metal except for said glass member and having seals only between said member, said eyelet and said conductor whereby said getter material is removed from all of the seals of said device and from all of the glass portions thereof.

11. An electric discharge device comprising an envelope containing an electrode structure, a leading-in conductor for said structure, said envelope being constituted entirely of metal except for a glass member of substantially smaller size than the size of the envelope, said conductor passing through said member whereby the conductor is insulated from the envelope, a pocket formed in said envelope and a getter material in said pocket.

' JAMES E. BEGGS. 

